The Morphology of the Stratospheric Polar Vortex Under Stratospheric Aerosol Intervention Scenarios

Even though it is widely acknowledged that the stratospheric polar vortex (SPV) strengthens under stratospheric aerosol intervention (SAI), little is known about how the SPV's size, duration, location, and edge change under SAI compared to the present-day climate. Here, we address these issues using two large ensemble SAI simulations, namely GLENS (2060–2079) with extreme forcing and ARISE (2050–2069) with more moderate forcing. It is found that the wintertime Arctic and Antarctic stratospheric wind responses to SAI compared to the control (CTL) climate in GLENS (2060–2079) are roughly two times as large as in ARISE (2050–2069). While the zonal wind acceleration in ARISE (2050–2069) is hemispherically symmetric at 3–4 m s⁻¹ in the stratosphere of both hemispheres, the responses in GLENS (2060–2079) are hemispherically asymmetric, being two to three times larger in the Southern Hemisphere (SH, ~15 m s⁻¹) compared to the Northern Hemisphere (NH). While the edge of the vortex in GLENS (2060–2079) intensifies under SAI, similar changes are not found in ARISE (2050–2069). Such intensification of the vortex edge in GLENS is limited to lower stratosphere levels and does not extend to greater heights (~10 hPa). SAI has no discernible effect on the NH vortex morphology in ARISE simulations. However, the edge of the vortex intensifies in terms of Ertel's potential vorticity (EPV) gradient under SAI in the NH in GLENS. The greatest change that the SPV consistently shows under SAI in both GLENS and ARISE simulations is the SH spring vortex's behaviour. Under SAI, at 530 and 600 K, the vortex edge is weaker, its area is smaller, and it breaks up earlier than in the CTL runs.